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Thread: May have just saved a battery

  1. #1
    Ean Austral Guest

    May have just saved a battery

    Gday All,

    A while back I fitted a seperate Alternator cable and run it thru a resettable 120amp circuit breaker because I had read of so many Alt failures resulting in a dead battery and a stranded car .
    wife gets home tonight and says the battery light is on , have a look and the Breaker was tripped , reset it and it tripped within 10 secs. Thought it might be a bit hot so left it for about 30mins and same thing.

    put the multi meter on and the lead from the Alternator is reading 18.7 volts. I will do some more checks tomorrow and I have a new Alternator if I need but it's looking like the old Alternator is pumping out way to many volts, and if so then my time and effort of fitting the seperate cable and C/B was worth it .

    off to see the Rugby League World Cup game so the checks will have to wait till tomorrow

    Cheers Ean

  2. #2
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    Possibly having saved your wife from being stranded somewhere at night may have been the main benefit.
    MY21.5 L405 D350 Vogue SE with 19s. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi, RTK base station using LoRa

  3. #3
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    May have just saved a battery

    Hmmm. I wonder if because the alternator is isolated (circuit breaker tripped), this is causing the high voltage with no load to bring it back down (infinite resistance versus a load). Just a consideration.
    Consider the circuit breaker may have also failed or specification failed such that it is tripping at less amperage.
    And maybe you’re right, the alternator’s failed.
    2010 TDV6 3.0L Discovery 4 HSE
    2007 Audi RS4 (B7)

  4. #4
    Ean Austral Guest
    Quote Originally Posted by Graeme View Post
    Possibly having saved your wife from being stranded somewhere at night may have been the main benefit.
    Gday Graeme, it was your original idea of fitting the seperate Alternator cable , so will see what I find today . The battery was at 12v so put it on charge just to make sure . It's now at 13.4 volts so no damage by the looks of it. Am about to go and start checking things and possibly doing an Alternator change . It's the original Alternator so it's a couple of months short of 10 yrs old and done 142,000ks

    it was peak hour in Toyota territory, reckon face book would have been flooded with pics of a Land Rover either stuck in the middlr of the road with the bonnet up , or being loaded onto a flat bed .

    Cheers Ean

  5. #5
    Ean Austral Guest
    Quote Originally Posted by DiscoJeffster View Post
    Hmmm. I wonder if because the alternator is isolated (circuit breaker tripped), this is causing the high voltage with no load to bring it back down (infinite resistance versus a load). Just a consideration.
    Consider the circuit breaker may have also failed or specification failed such that it is tripping at less amperage.
    And maybe you’re right, the alternator’s failed.
    i have a seperate set up that takes a fuse , I had that in for a while , so I am going to fit that first and see if it blows the 100amp fuse it still has in it . I had that in the car originally but it's not very easy to mount it due to its size.

    the fact that the cable from the Alternator is showing 18 plus volts makes me think it's the Alternator voltage regulator that has failed. I did read somewhere that if you get 140,000ks out of the Alternator you have done well , but that could be 1 workshops opinion.

    Cheers Ean

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    Quote Originally Posted by Ean Austral View Post
    i have a seperate set up that takes a fuse , I had that in for a while , so I am going to fit that first and see if it blows the 100amp fuse it still has in it . I had that in the car originally but it's not very easy to mount it due to its size.

    the fact that the cable from the Alternator is showing 18 plus volts makes me think it's the Alternator voltage regulator that has failed. I did read somewhere that if you get 140,000ks out of the Alternator you have done well , but that could be 1 workshops opinion.

    Cheers Ean
    242,000km out of mine so far (D4). I have however ordered a new one and will be fitting it in the next few weeks as I don’t like tempting fate. Good luck with the search for the issue
    2010 TDV6 3.0L Discovery 4 HSE
    2007 Audi RS4 (B7)

  7. #7
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    May have just saved a battery

    I’ll only add that I’d have thought the circuit breaker would be relatively agnostic to the voltage difference (~14V to ~18V) and I don’t believe the increase in voltage will cause a current increase (normally the opposite) so for a current sensing device to trip for that I’d be keeping an open mind. As you say, maybe try the fuse and measure voltages etc.
    2010 TDV6 3.0L Discovery 4 HSE
    2007 Audi RS4 (B7)

  8. #8
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    Quote Originally Posted by DiscoJeffster View Post
    242,000km out of mine so far (D4). I have however ordered a new one and will be fitting it in the next few weeks as I don’t like tempting fate. Good luck with the search for the issue

    242,000 kms!

    D4 3.0 twin turbo?

    Any engine issues? Original engine?

    Regards

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    Quote Originally Posted by northiam View Post
    242,000 kms!

    D4 3.0 twin turbo?

    Any engine issues? Original engine?

    Regards
    Yep, 3.0 twin diesel.
    Turbine actuator replaced
    Drivers side intake manifold
    The other usual disco issues
    On original gearbox build
    2010 TDV6 3.0L Discovery 4 HSE
    2007 Audi RS4 (B7)

  10. #10
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    Quote Originally Posted by DiscoJeffster View Post
    242,000km out of mine so far (D4).
    A 3.0 alternator rather than a 2.7 one - 60A diodes vs 50A diodes.
    MY21.5 L405 D350 Vogue SE with 19s. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi, RTK base station using LoRa

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